Oedipus
Ah, ah, lady, why should one look to the prophetic hearth of Pytho, or to the birds that shriek above us, according to whose message I was to kill my father? But he is dead, and lies deep below the earth; and I am here, not having touched the weapon, unless he died from missing me; in that way I might have caused his death. But still, Polybus lies in Hades, and with him have gone the oracles that were with us, now worth nothing.
H. Lloyd-Jones 1994

Oedipus
Alas, alas! Why indeed, my wife, should one look to the [965] hearth of the Pythian seer, or to the birds that scream above our heads, who declared that I was doomed to slay my father? But he is dead, and lies beneath the earth, and here I am, not having put my hand to any spear—unless, perhaps, he died out of longing for me: [970] thus, indeed, I would be the cause of his death. But as the oracles stand, at least, Polybus has swept them with him to his rest in Hades. They are worth nothing.
R C Jebb

Geoffrey Steadman has the following note on δὴ Soph. OT 968

"δὴ: temporal, equiv. to ἠδὴ"

Looking into this a little, I discovered that Jebb, Dawe, Cooper, Smyth all have comments on κάτω δὴ Soph. OT 968. Jebb's student edition says very little, "Here δὴ nearly = ἠδὴ" see also Smyth §2845. Cooper argues against the temporal use of δὴ. He argues that δὴ calls attention to and reinforces the preceding word in this case the adverb κάτω. That is an over simplification of Cooper's argument which is well nuanced and and much longer than the others (Greek Syntax, vol 4, 2:69.18.2.J, p. 2944 ). Cooper's major treatment of the subject is in vol 2 of Attic Syntax, 1:69.17.0 p1307ff where he interacts with Denniston's discussion of δὴ. R.D. Dawe:1982 p.194 gives a nod toward Jebb/Smyth but leans the other direction.